An apparatus for the production of spun-bond can comprise a spinneret, a cooling chamber into which processing air for the cooling of the filaments can be introduced from an air supply chamber, a stretching unit having a lower draft channel and having a deposit or collections unit for depositing the filaments for the non-woven fibrous web or mat. The term “processing air” defines cooling air for cooling the filaments.
A known arrangement of the type is described in (DE 196 20 379 C2 and U.S. Pat. No. 5,814,349), which this invention is based upon. This apparatus is generally proven for the production of a non-woven fibrous web made from aerodynamically stretched filaments. In this arrangement the stretching unit is aerodynamically decoupled from a tiering system (i.e. a system for laying down the filaments in overlapping relationship), which is provided with a diffuser. Here, a clear functional separation of the stretching unit and from the tiering unit exists.
For this purpose, the lower draft channel, with respect to the thickness of the gap, is embodied as a barring air shaft aerodynamically separating the tiering unit from the stretching unit. The term “barring air shaft” means that during operation the lower draft channel continuously releases processing air, which enters the diffuser. However this air has a mass flow and kinetic energy which prevents pressure changes in the tiering unit from causing disturbing affects on the aerodynamic conditions in the air flow system and/or in the cooling chamber and vice versa. Therefore, in this arrangement the cooling process and/or the air flow process in the cooling chamber can be optimized without interfering with the optimization of the tiering process and thus, the formation of the non-woven fibrous web.
On the other hand, the tiering system can be optimized with respect to the formation of the non-woven fibrous web, without subjecting the air flow system and/or the cooling system to interference.
The cooling chamber of this arrangement allocated underneath the spinneret is additionally provided with an air flow blower by which the processing air for cooling the filaments is blown onto the filaments. However, when the speed of the filaments and the fineness of the filaments is to be increased (e.g., reducing the titers to values distinctly lower than 1), arrangements of the known type reach their limits. The air flow in this arrangement is not suitable for higher throughputs, because problems arise in the formation of the filaments. The resulting self-movement of the filaments leads to the filaments moving toward each other and thus, they can only be deposited in the form of filament bundles. Increasing the air speed in the arrangement described in order to increase the filament speed leads to an intensified cooling of the filaments. This intense cooling causes a premature solidification of the filaments and thus limits the filament speed and/or the filament fineness.